Tooth facing and backing therefor



Jan 12, 1943- c. L. MoRRls 2,308,195

TOOTH FACING AND BACKING THEREFOR Filed June '7, 1940 i l. IIIIIMIHIF w ATTORNEYS Patented Jan. l2, 1943 UNET l stares Ohio, assigner to The Columbia Dental Manufacturng Company, Columbus, Ohio, a corporation of Ohio Application June 7, 1940, Serial No. 339,368

2 Claims.

This invention relates to tooth facings and backings therefor. It has to do particularly with those types of facings and backings which are designed for the formation of anterior' articial teeth in bridgework. It is particularly designed for the provision of a backing and a removable facing to be mounted thereon, which backing and facing are so constructed that, in combination, there is produced a porcelain biting edge.

There has long been a need in the art of interchangeable facings for use in bridgework for a combined backing :and facingv wherein there results an integrally formed porcelain biting edge which is relatively translucent and which is, at

the same time, so constructed and supported that it Will have adequate strength. A number of patents have been issued which show interchangeable facings with integrally formed porcelain biting edges. However, these patents disclose structures which are impracticable either from the standpoint of inadequate strength or support or from the standpoint of appearance. As a matter of fact, as far as is known, there are no tooth facings being commercially marketed in which the attempt is made to render the incisal edge of the facing translucent.

In these particular prior art devices which are being marketed, there are certain defects, both from the standpoint of the structureof the facing and from the standpoint of the manner of mounting such facing, which practically defeat the end sought, namely, relative translucence of the incisal edge of the to-oth. For example, the removable facing is made of a composite structure embodying a comparatively opaque portion and a partially overlying translucent portion. In addition, that part of the comparatively translucent portion which does not overlie the relatively opaque portion of the facing does overlie the incisal edge of the backing which terminates coincident with the incisal edge of the facing. Thus, that part of the comparatively translucent portion of the facing, which overlies the comparatively opaque portion of such facing, is'rendered relatively ineffective by such opaque `portion of the facing while that part of the comparatively translucent portion of the facing, Which overlies the incisal edge of the backing, is rendered relatively ineffective from the standpoint of translucence by the backing as well as by the interposed cement which must be used to effect retention of the facing upon the backing. These features result in substantially defeating the purpose of the translucent portion of the facing which, as stated, is to provide an artificial tooth whichrwill be more pervious to light and which will consequently more nearly simulate the natural tooth.

One of the objects of this'invention is to provide tooth facings for anterior teeth in bridgework which will have their incisal edges relatively translucent in comparison with the other portions of the facings.

Another object of this invention is to provide combined facings and backings for anterior teeth in bridgework of such relative structures and mountings that there Will result porcelain biting edges, which combined structures will not only be relatively translucent but which will be of adequate strength to resist the pressures `to which they will be subjected in use.

Another object of this invention is to provide combined facings and backings for anterior teeth in artificial bridgework of such relative structures and mountings that the porcelain biting edges thereof will be of adequate thickness to offset the comparative brittleness which is inevitably characteristic of the material which must be utilized to obtain the translucence desired.

This invention consists in the provision of a facing for use in anterior teeth forbridgework which embodies an incisal edge that is translucent throughout its depth or thickness in comparison with the main body of the tooth facing of which it forms an integral part. It further consists in the provision of such a facing and of a backing for use in combination therewith, which facing and backing will be complementally formed so that the incisal edge of the facing will overlie the incisal edge of the backing to produce an artificial tooth having a porcelain biting edge. Moreover, this complemental formation is such that the part of the translucent incisal edge portion of the facing which overlaps the incisal edge of the backing will be adee quately supported by the backing against the pressures in use which might tend to cause breakage thereof if such portion were left unsupported.

This invention may take various forms and some of these forms are shown in the -accompanying drawing wherein similar characters of reference designate corresponding parts and wherein:

Figure 1 is a front elevation disclosing the labial f-ace of an anterior interchangeable tooth facing made in accordance with this invention.

Figure 2 is a rear elevation of the lingualface of the tooth facing shown in Figure 1.

Figure 3 is a side elevation of the interchangeable facing shown in Figures 1 and 2.

Figure 4 is a section taken on line 4 4 of Figure 2 looking from the gingival towards the incisal edge of the facing.

Figure 5 is a section, similar to that shown in Figure 4, of a tooth facing wherein the cross section of the post hole and slot is of T-shaped or angular form. f

Figure 6 is a rear elevation showing the lingual side of a modified form of the tooth facing.

Figure 7 is a rear elevation showing the lingual side of another modied form of the tooth facing.

Figure 8 is a section taken along line 8 8 of Figure 7 of a tooth facing, made in accordance with this invention, with a change as to detail.

Figure 9 is a vertical section of a tooth facing, made in accordance with this invention, but ernbodying a still further modification in detail.

Figure 10 is a rear elevation showing the lingual side of a tooth facing, made in accordance with this invention, wherein the portion of the incisal edge of the facing which overlaps the incisal edge of the backing is grooved to receive said incisal edge of the backing.

Figure 11 is a section taken online ii-II of Figure 10.

Figure 12 is a rear elevation showing the lingual face of a tooth facing, made in accordance with this invention, with slight modiiications from the forms previously shown.

Figure 13 is a perspective View of a backing which is designed for usewith a tooth facing of the type shown in Figure 8.

Figure 14 is a vertical longitudinal section showing the tooth facing of Figures 7 and 8 with the backing of Figure 13 applied thereto.

Figure 15 is a perspective View of a novel type of backing wherein the rib and post are formed integrally with the backing proper.

Figure 16 is a vertical longitudinal section of a facing which is designed to be combined with the backing of Figure 15.

Figure 17 is a. perspective view showing the backing of Figure 15 and the facing of Figure 16 in assembled relation.

Referring specifically to the drawing and more particularly to Figures 1 to 4, inclusive, it will be seen that the labial side of the tooth I is of usual form but that the lingual side of the facing is provided with a shelf or shoulder 2 which is of convex form in its mesio-distal extension and which projects outwardly from a fiat face 3 communicating at its upper end with a curved ridgelap 4. In the facing 3 there is provided a longitudinal slot 5 which communicates at its rear with a longitudinal post hole E5 whose diameter is greater than the width of said slot. It will also be noted that the post hole 6 is of greater length than the slot 5 and that it projects downwardly into the incisal edge of the tooth for a slight or substantial distance below the shoulder 2.

The manner in which this facing is utilized will be readily understood, since it is combined with a backing which is provided with a post connected to the body of the backing by a web or rib. Such a combination is illustrated in Figure 17, with the exception that the incisal edge of the backing will be of concave form so that it will be complementary to the convex shoulder 2 of tl e facing.

The fact that the post hole 6 extends incisally beyond'the shoulder 2 results in an interlocking engagement of greater strength between the facing and the backing to prevent the facing from being displaced in a labial direction. The formation of the facing with the shoulder 2 serves to strengthen the central area of the tooth against longitudinalV fracture. Furthermore, this form of shoulder permits the use of a greater amount of Solder when assembling one tooth and backing with another in bridge construction. Likewise,

shoulders of this shape permit the backing to extending closer to the incisal edge along the lateral margins of the tooth and thus permit flowing of solder likewise in this direction, thus giving additional reinforcement to the assembled bridge structure.

In the form shown in Figure 5, the structure of the facing is identical with that previously described with one exception. This exception consists in the fact that the post hole II and the slot I2 when taken together form a T-shaped structure. While the cylindrical post hole, shown in Figures l to 4, inclusive, offers certain advantages of manufacture, nevertheless, the T- shaped post hole and slot appreciably add .to the retentive strength between the tooth facing and its backing member.

In the form shown in Figure 6, the facing is substantially identical with theY form .shown in Figures 1 to 4, inclusive,'with one exception. This exception consists in the form of the shoulder or shelf which, instead of being convex in form; is provided with a flat upper surface I3 with downwardly and outwardly curved ends I4. The result is that the shoulder, as a whole, is of straight line construction in the central portion of the tooth and is intersected at each end by arcuate supplemental shoulders which extend somewhat obliquely towards the incisal end of the tooth.

It will be understood that the backing for the tooth facing shown in Figure` 6 is to be com'ple- Y mentally designed so that the incisal edge thereof is provided with a central straight line portion and with downwardly and outwardly curved wings, so that it will have a snug fit with the surfaces I3 and I4 of the shoulder of the tooth facing. Shoulders of this shape not only strengthen Y the central area of the tooth facing against longitudinal fracture, but they permit'the use cfa greater amount of solder when' assembling one tooth and backing with another in bridgelconstructi0n.. Shoulders of this shape also permit the backing to extend .closer to the incisal edge along the lateral margins of the tooth and permit the flowing of solder likewise in this direction, thus giving additional reinforcement to-the assembled bridge structure. A i m In the form of facing shown in Figures 7 and 8, it will be noted'that the facing is substantially identical with that shown in Figures' 1 to 4, inclusive, with certain exceptions. These exceptions consist in the -fact that the shoulder I5wis of straight line or at form for the full widthof the tooth and in' the fact that thisl fiat surface is connectedto the at Vsinglesurface I6 of -the tooth facing by an arcuate surface I1. This arcuate surface II adds strength to the facing structure in thatit does not present the natural lines of cleavage that 'are inherent kwhere such surfaces are joined at a 'degree angle. VIt will also bel noted by Vreference to Figure 8 that lthe facing is formed in two layers, the layer 3a co'nstituting the body portion and the layer 3b constitutingthe enameled portion which is blended with the body portion, which is relativelytranslucent and which extends Ybeyond the body por"- tion at the incisal edge of the facing.

'I'he form of facing which is shown in Figure 9 is substantially identical with the form shown in Figures 7 and 8, with certain exceptions. One exception consists in the fact that the incisal end of the slot terminates gingivally of the shoulder I3, as at I9. Another exception consists in the fact that the labial side of the post hole converges lingually, near its incisal end, as at 20. By terminating the incisal end of the slot gingvally of the shoulder, the tooth facing is strengthened so that its resistance to longitudinal pressure in its central area is increased, since this makes it possible to provide a greater bulk of porcelain in the area adjacent to the shoulder and lingual to the incisal end of the post hole. It will be understood that the obliquely disposed portion 2U of the post hole requires that the post on the backing have a correspondingly chamfered incisal end so that it will t snugly in the bottom of the post hole. One advantage of this construction is that in some of the smaller and thinner teeth it prevents the bore and the post from showing through the labial surface of the tooth facing. It is appreciated by those skilled in the art, that dental porcelain has always been somewhat translucent to a greater or lesser degree in order to have the artificial teeth appear more natural. incisal end of the post hole and the post permits the use of more porcelain body for covering the end of the bore without detracting from the strength of the attachment means. However, it

will also be noted that the facing is formed in i two layers, the layer 3a constituting the body portion and the layer 3b constituting the enameled portion which is blended with the body portion, which is relatively translucent and which extends beyond the body portion at the incisal edge of the facing.

In the form shown in Figures l and 11, the structure is substantially identical with the forms shown in Figures 7 and 8 with certain exceptions. One exception consists in the fact that the flat plane 2l of the lingual side of the tooth facing extends beyond the shoulder 22 in the direction of the incisal edge of the tooth to form a kerf 23. The backing is constructed complementally so that it extends into and fits snugly in the kerf 23. This gives an additional reinforcement to the incisal edge of the tooth facing, which reinforcement extends throughout the width of the tooth. This construction materially relieves the strain on the incisal end of the post when the stresses of mastication are in a labial direction. Another exception consists in the fact that the flat surface 2| is connected to -the shoulder 22 by an angular instead of an arcuate surface such as shown at l1 in Figure 8. It will also be noted in Figure 11 that the facing is formed in two layers, the layer 3a constituting the body portion and the layer 3b constituting the enameled portion which is blended with the body portion, which is relatively translucent and which extends beyond the body portion at the incisal edge of the facing.

In the form shown in Figure 12, the shoulder 24 is convexly curved in a manner similar to the shoulder 2 in Figure 2. However, there is a kerf 25 whose base is of concave curvature. This kerf is designed to receive an extension which is formed on the backing which serves as a reinforcement for the tooth facing in addition to the post of the backing.

This oblique construction of the i It will be noted that in the structures shown in Figures 10, 1l vand 12, the incisal ends of the backing and the post cooperate to embrace a part of the porcelain of the incisal end of ther facing. provides a dual reinforcement which adds to the strength of the tooth as a whole.

In the form shown in Figures 13 and 14, the backing is of two-piece construction, with a rib and post l2% and 2l combined with the backing proper 2B by means of rivets 2e which are formed upon the rib and project through the backing 28. One or more rivets may be utilized depending upon the required length of the backing. It will be noted that the lower end of the backing is vprovided with a flange et that rests upon the shoulder l5 of the tooth facing. It will also be noted that there is a clearance between the lower end of the post 2l and the bottom of the post 'hole and that there is a clearance between the lower end of the rib 25 and the bottom of the slot in which it nts. Thus, the stresses which are applied longitudinally of the tooth facing will be transmitted directly through the shoulder I5a to the flange 3d ofthe backing. It is a feature of this invention that this flanged vlower end of the backing proper @ti is equally spaced from the incisal edge of the tooth facing regardless of the length of such tooth facing and that this construction in combination with the clearances between the bottom of the slot and the rib and between the bottom of the post hole and the post will result in a rigid supporting contact which will avoid any tendency toward central fracture of the tooth facing. Obviously, this feature is applicable Whether a two-piecebacking is utilized or Whether a one-piece backing is utilized.

Consideration of Figure 14 will show that the facing is like that of Figures 7 and '8, rbeing formed in two layers, the layer 3a constituting the body portion and the layer 3b constituting the enameled portion, which is relatively translucent Vand which extends beyond the body portion at the incisal edge of the facing. Likewise, it will be seen that the portion of the layer 3b which extends beyond the body portion at the incisal edge of the facing is likewise substantially beyond the incisal end of the backing so that its translucence is not impaired thereby.

Figure 15 shows a one-piece backing embodying a post 3l and a rib 32 integrally connected to a backing proper 33. This backing proper 33 has a flange 34 at the incisal edge which is preferably inclined to an angle of about degrees. Figure 16 shows a tooth facing 35 having a post hole 35, a slot 3l and a shoulder 38. It will also be noted that the facing is formed in two layers, the layer 3a constituting the body portion and the layer 3b constituting the enameled portion which is blended with the body portion, which is relatively translucent and which extends beyond the body portion at the incisal edge of the facing. The shoulder 38 is designed to make contact with the flange 34 when the parts of Figures 15 and 16 are assembled, While there remains a clearance between the bottom of the post and the bottom of the post hole and there also remains a clearance between the bottom of the rib and the bottom of the slot in which it fits. As in the construction described in Figures 13 and 14, the distance between the shoulder38 and the incisal edge of the tooth facing will be identical in two facings of different lengths. Figure 17 illustrates the backing of Figure 15 and the facing of Figure 16 in assembled relation.

From the above description, it will be seen that a novel type of tooth facing is provided'for use in bridge structures together With a novel'type of backing for cooperation therewith and that the combination is also novel. As explained in connection with the description of FigureV 14, there is provided a tooth facing with an incisal edge which is relatively translucent in comparison with the major portion of the tooth facing in combination with a backing for cooperation with the tooth facing which is of such a structure and which so carries the tooth facing that the translucent incisal edge thereof is not overlapped by the backing, which combination insures greater translucence of the incisal edge of the tooth facing. In addition, it Will be noted that this facing overlaps the incisal edge of the backing and, consequently, is of a thickness greater than that normally found in facings, particularly at the incisal edge thereof. Furthermore, it will be noted that a tooth facing is provided of such a structure and complemental backing therefor that there is produced increased reinforcement to the facing as Well as increased area upon which the solder may be flowed when the backing units are connected together to form the bridge structure. In certain forms of this backing, the reinforcing action is accentuated by the fact that the backing and the post cooperate to embrace a portion of the porcelain found on the incisal edge. of the facing, its structure and the structure of the backing serve to give additional reinforcement to the incisal edge of the facing which, being of a material which is relatively translucent, is inevitably of a more brittle nature.

Having thus described this invention, what is claimed is:

1. The combination of an interchangeable tooth facing and backing therefor, said facing having a flat surface and a shoulder on the lingual side thereof connected to each other by a concave arcuate surface, said facing having a longitudinal bore of substantially uniform crosssection formed therein adjacent said flat surface and extending from the gingival end thereof toward the'incisal end of said facing to a point The manner of the mounting short of the incisal end of said Yfacing and hav-` ing a slot of less width than the Width of said bore communicating with said bore and opening it to said nat surface but 'terminating incisally short of the end of said bore, said backing comprising a flat body portion having an inner surface disposed in contact with said flat surface of said tooth facing, said backing carrying a 1ongitudinally extending post onits inner surface which is of substantially uniform cross-section complemental to said bore and which is connected to said body portion by means of a vlongitudinally extending rib complemental to said slot, a ange formed on the incisal edge of said body portion and being of convex form to cooperate with said concave surface on said tooth facing, said post and said rib terminating short of the incisal ends of said bore and said slot, with which they cooperate, when said flange is in contact with said arcuate surface.

c 2. The combination of an interchangeable tooth facing and backing therefor, said facing having a longitudinally extending surface on the lingual side thereof which has a transversely extending lingually projecting bearing surface adjacent the incisal edge thereof, said facing having a longitudinally extending mortise formed therein adjacent said lingual surface and extending from the gingival end of said facing toward the incisal end of said facing, said backing comprising a body portion having an inner surface disposed in contact with said lingual surfaceV of said tooth facing, said backing carrying a longitudinally extending tenon on its inner surface which is complemental to said mortise, a transversely extending bearing portion formed on said body portion adjacent the incisal edge thereof and being complemental to said bearing surface on said tooth facing to cooperate therewith, said tenon terminating short of the incisal end of said mortise in said facing when said bearing portion is in contact with said bearing surface.

Deceased.

I CRRTIFICATROR CORRECTION.

Patent No. 2,508,195. January. l2, 19.1.5,

CHARLES LEON MORRIS, DECEASED, BY MARIE C. MORRIS, EMECUTRIX.

Itis' herebyl certified that the name of the assignee-in the above numbered patent was erroneously descr-ibedand specified as The Columbia Dental Manufacturing Company whereas said name should have been described and specified as --The Columbus Dental Manufacturing Company, 'of Columbus, Ohio`, a oorporationof Ohio",l as shown by the record of assignments in this office; page 2, second column, line ll, for the word "extending" read "extend-'1l and thatthe said Letters Patent should be Ieadwth this correction therein that the same may conform to their-ecord of`the case in the Patent Office. I

Signed and sealed this 25rd day of February., A. D. 19H5( 4 1 -Henry van Arstale, (Seal) Acting Commissioner .of Patents. 

